This invention generally relates to a linear peristaltic pump for the IV administration of parenteral fluids such as saline and drug solutions, and for enteric administration of fluids such as liquid nutrients.
One of the most important aspects of the administration of parenteral fluids is controlling the fluid flow rate to the patient. In prior practices where the fluid was drained from an inverted bottle and fed by gravity through a clear plastic IV tube to the patient, fluid flow was usually controlled by adjusting the position of a roll clamp on the IV tube. The fluid flow rate was determined by counting the fluid drops in a drip chamber over a period of time and then, if needed, the position of the roll clamp was adjusted to obtain the desired flow rate. However, this gravity fed administration system was subject to large flow rate variations due to changes to the liquid level in the bottle, changes in the temperature of the fluid, changes in the venous or arterial pressure in the patient, patient movement and drift in the effective setting of the roll clamp. As a result, frequent monitoring by medical personnel was required and variations were still encountered.
Electronic pump systems and drop flow controllers for gravity systems helped in maintaining a desired flow rate of parenteral fluids to the patient and such systems are now in widespread use. As the mechanical arts were developed, new applications have evolved which have placed more difficult demands on the delivery systems. As a consequence, the need for improvement continues to exist.
Prior pumping systems, particularly linear peristaltic pumping systems, provided a much more consistent fluid flow, particularly with viscous fluids which were not readily controllable in a gravity administration system. Typical pumping systems now in use have a plurality of cams, an equal number of cam actuated fingers or cam followers and a pressure pad adapted to receive a flexible tube and urge the tube against the fingers or cam followers. When the fingers or cam followers were sequentially actuated by the cams, the individual fingers would deform and close off the tube at a plurality of sequential points along the length of the tube to thereby force fluid in the tube along the length thereof.
While the prior linear peristaltic pumping system described provided a more consistent fluid flow than with the roll clamp approach, the energy requirements for pumping were relatively high because of the friction between the fingers themselves and between the fingers and the cams which activate the fingers. Additionally, the prior systems characteristically had a relatively low pump efficiency because of leakage or backflow of fluids.
Moreover, it is required that the fingers exert sufficient force to achieve delivery under a number of variable conditions. These conditions relate to entering stiffness, the viscosity of the fluid being delivered and the resistance of the patient's system. In addition, it is desirable to limit the pressure developed in the delivery system should an occulsion occur in that system, such as from a kinked tube.
It is evident that there is a recognized need for a relatively simple peristaltic pump which has high mechancial and pumping efficiencies which will deliver fluids accurately within desired operating limits. The present invention satisfies these needs.